The present invention relates to a bi-directional valve and, more particularly, to a bi-directional vent and overpressure relief valve for use with closed fuel tank systems.
Current environmental regulations for automobiles require that the fuel tank be provided with an evaporation system in order to properly contain gases given off by fuel for the automobile. For example, when the fuel tank heats up, such as on a hot day, the vapor pressure within the tank may increase quickly requiring a pressure release system to allow passage of vapors from the tank without releasing the vapors directly into the surrounding environment.
Accordingly, a pressure release or evaporation system is provided for the fuel tank wherein gases from the fuel tank are routed through a filter canister, such as a carbon filter, to the engine. In addition, gas flow may also take place in a direction from the engine to the fuel tank in order to avoid the formation of a vacuum in the fuel tank as the fuel tank cools or as the fuel level decreases during operation of the engine.
In order to control the gas flow to and from the fuel tank, a valve is provided located between the fuel tank and the filter canister. In this regard, there is a need for a valve which limits flow of gases in either direction between the fuel tank and the engine such that gases will flow to the engine upon the build-up of pressure to a predetermined level within the fuel tank, and gases will flow from the engine to the fuel tank when a predetermined vacuum is present within the fuel tank.
In addition, there is a need for such a valve in which the valve will provide an overpressure relief function when a substantially high pressure is produced within the fuel tank to thus provide a quick pressure release.